Polyether dihydroxyalkyl carbamate epoxy additive for epoxy resins

ABSTRACT

The adhesion properties of amine-cured epoxy resins are unexpectedly enhanced by addition of certain di-hydroxyalkyl carbamate terminated polyether additives. The adhesively superior epoxy resin composition comprises a vicinal polyepoxide, a curing amount of an amine curing agent, and an effective amount of a polyether dicarbamate having terminal hydroxyalkyl carbamate groups and a molecular weight of from about 2000 to about 3000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to curable epoxy resins having increased adhesivestrength; and, more particularly, to amine cured epoxy resins containingcertain di-hydroxyalkyl carbamate terminated polyether additives.

2. Prior Art

Epoxy resins constitute a broad class of polymeric materials having awide range of physical characteristics. The resins are characterized byepoxide groups which are cured by reaction with certain catalysts orcuring agents to provide cured epoxy resin compositions with certaindesirable properties. One such class of curing agents are generally theamines. The most commonly used amine curing agents are aliphatic aminessuch as diethylenetriamine, triethylenetetramine and the like and/orpolyoxyalkylene polyamines; such as polyoxypropylene diamines andtriamines.

Epoxy resin compositions having impproved physical properties areobtained by employing polyoxyalkyleneamines, and polyoxyalkylenediaminesin particular, as curing agents. It is common to employ with such epoxyresin compositions a co-curing agent such as those described in U.S.Pat. No. 3,549,592.

Also known to be effective as epoxy curing agents or co-curing agentsare various ureas and substituted ureas, such as those disclosed in U.S.Pat. Nos. 3,294,749; 2,713,569; 3,386,956; 3,386,955; 2,855,372 and3,639,338. The ureas disclosed in the above references are useful aseither curing agents or as curing accelerators.

It has now been unexpectedly found that a specific di-hydroxyalkylcarbamate terminated polyoxyalkylene material having a molecular weightof from about 2000 to about 3000, when employed as an epoxy additive,provides cured epoxy resin compositions exhibiting outstanding strengthof adhesion. Specifically, epoxy resins incorporating these additives,upon curing with an amine, provide a material with high tensile shearstrength and superior adhesion to substrates.

SUMMARY OF THE INVENTION

According to the broad aspect of the instant invention, the adhesivestrength of amine-cured epoxy resins is enhanced by the addition of aneffective amount of a polyether carbamate having terminaldi-hydroxyalkyl carbamate groups and having a molecular weight of from2000 to about 3000.

In one aspect, a curable epoxy resin composition having superioradhesive strength comprises a vicinal polyepoxide, a curing amount of anamine curing agent and an effective amount of the polyether di-carbamateadditive.

In accordance with a preferred embodiment, a diglycidyl ether of4,4'-isopropylidene bisphenol, a curing amount of a primaryamine-containing curing agent consisting essentially of apolyoxypropylene polyamine having a molecular weight of from about 200to 500, a piperazine-amino alkanol accelerator and an effective amountof a polyether dicarbamate having terminal hydroxyalkyl carbamate groupsand a molecular weight of about 2000 are utilized to form a resin.

DETAILED DESCRIPTION OF THE INVENTION

According to the instant inventive concept, blends of a polyepoxide, anamine curing agent and the di-hydroxyalkyl carbamate terminatedpolyether containing compounds and, optionally, an accelerator arethoroughly admixed and cured in accordance with conventional methods toprovide cured epoxy resins having unexpectedly superior adhesivestrength.

Generally the vicinal polyepoxide containing compositions which areamine cured are organic materials having an average of at least 1.8reactive 1,2-epoxy groups per molecule. These polyepoxide materials canbe monomeric or polymeric, saturated or unsaturated, aliphatic,cycloaliphatic, aromatic or heterocyclic, and may be substituted ifdesired with other substituents besides the epoxy groups, e.g., hydroxylgroups, ether radicals, aromatic halogen atoms and the like.

Preferred polyepoxides are those of glycidyl ethers prepared byepoxidizing the corresponding allyl ethers or reacting, by knownprocedures, a molar excess of epichlorohydrin and an aromaticpolyhydroxy compound, i.e., isopropylidene bisphenol, novolak,resorcinol, etc. The epoxy derivatives of methylene or isopropylidenebisphenols are especially preferred.

A widely used class of polyepoxides which are useful according to theinstant invention includes the resinous epoxy polyethers obtained byreacting an epihalohydrin, such as epichlorohydrin, and the like, witheither a polyhydric phenol or a polyhydric alcohol. An illustrative, butby no means exhaustive, listing of suitable dihydric phenols includes4,4'-isopropylidene bisphenol, 2,4'-dihydroxydiphenylethylmethane,3,3'-dihydroxydiphenyldiethylmethane,3,4'-dihydroxydiphenylmethylpropylmethane,2,3'-dihydroxydiphenylethylphenylmethane,4,4'-dihydroxydiphenylpropylphenylmethane,4,4'-dihydroxydiphenylbutylphenylmethane,2,2'-dihydroxydiphenylditolylmethane,4,4'-dihydroxydiphenyltolylmethylmethane and the like. Other polyhydricphenols which may also be co-reacted with an epihalohydrin to providethese epoxy polyethers are such compounds as resorcinol, hydroquinone,substituted hydroquinones, e.g., methylhydroquinone, and the like.

Among the polyhydric alcohols which can be co-reacted with anepihalohydrin to provide these resinous epoxy polyethers are suchcompounds as ethylene glycol, propylene glycols, butylene glycols,pentane diols, bis(4-hydroxycyclohexyl)dimethylmethane,1,4-dimethylolbenzene, glycerol, 1,2,6-hexanetriol, trimethylolpropane,mannitol, sorbitol, erythritol, pentaerythritol, their dimers, trimersand higher polymers, e.g., polyethylene glycols, polypropylene glycols,triglycerol, dipentaerythritol and the like, polyallyl alcohol,polyhydric thioethers, such as 2,2'-, 3,3'-tetrahydroxydipropylsulfideand the like, mercapto alcohols such as monothioglycerol,dithioglycerol, and the like, polyhydric alcohol partial esters, such asmonostearin, pentaerythritol monoacetate, and the like, and halogenatedpolyhydric alcohols such as the monochlorohydrins of glycerol, sorbitol,pentaerythritol and the like.

Another class of polymeric polyepoxides which can be amine cured and arein accordance with the instant invention includes the epoxy novalakresins obtained by reacting, preferably in the presence of a basiccatalyst, e.g., sodium or potassium hydroxide, an epihalohydrin, such asepichlorohydrin, with the resinous condensate of an aldehyde, e.g.,formaldehyde, and either a monohydric phenol e.g., phenol itself, or apolyhydric phenol. Further details concerning the nature and preparationof these epoxy novalak resins can be obtained in Lee, H. and Neville,K., Handbook of Epoxy Resins, McGraw Hill Book Co., New York, 1967.

It will be appreciated by those skilled in the art that the polyepoxidecompositions which are useful according to the practice of the presentinvention are not limited to those containing the above describedpolyepoxides, but that these polyepoxides are to be considered merely asbeing representative of the class of polyepoxides as a whole.

The amine curing agents which can be utilized in accordance with theinstant invention are generally any of those amine curing agents whichare well known to be useful for the curing of vicinal epoxides.Generally, those curing agents having at least three reactive aminohydrogens are useful.

Exemplary of those amines which can be utilized are alkylene polyaminessuch as diethylene triamine, triethylene tetramine and the like;oxyalkylene polyamines such as polyoxypropylene, di- and triamine anddiamino derivatives of ethylene glycol, such as 1,13-diamino4,7,10-trioxatridecane.

Additionally, aromatic amine curing agents are useful, such as thealkylene-linked polyphenyl amines, phenylene diamines and polycyclic orfused aromatic primary amine compounds. Additionally the correspondingcycloaliphatic compounds can be used.

Likewise, the polyamide curing agents such as the condensation productsof polyamines and polycarboxylic acids are useful. Suitable such amidecompounds are, for example, the condensation product of a polyamine anda dimerized fatty acid produced in accordance with U.S. Pat. No.2,379,413.

Of the amine curing agents known to be effective in curing a vicinalepoxy resin, preferred curing agents in accordance with the instantinvention are the polyoxyalkylene containing amine compounds. Apreferred class of polyoxyalkylene polyamines is depicted by theformula: ##STR1## wherein X is hydrogen, a methyl radical or an ethylradical; Z is a hydrocarbon radical having 2 to 5 carbon atoms formingfrom 2 to 4 external ether linkages; n is a number from 1 to about 15and r is a number from 2 to 4. The most preferred polyoxyalkylenepolyamines are the polyoxypropyl diamines wherein X is a methyl radical,n is a number from 1 to 10, Z is a 1,2-propylene radical and r is about2. These polyoxyalkylene polyamines can be prepared by known methods asdisclosed in U.S. Pat. Nos. 3,236,895 and 3,654,370. The most preferredpolyoxyalkylene polyamine is a polyoxypropylene diamine having amolecular weight of about 230.

Another preferred class of polyoxyalkylene polyamines can be depicted bythe formula: ##STR2## wherein X, Z, n and r are defined as above and yis 2 or 3. These poly(aminoalkylamino)polyethers are the hydrogenatedproduct of the cyanoalkylated adduct of a polyoxyalkylene polyamine asabove described. The preparation of the cyanoalkylated adducts isdescribed in U.S. Pat. No. 3,666,788 issued to Rowton, May 30, 1972.

Preferred such compounds are the hydrogenated cyanoethylatedpolyoxypropylene triamines.

The dicarbamate terminated polyether additive can generally be describedas polyoxyalkylene containing materials having terminal hydroxyalkylcarbamate groups and a molecular weight of from about 2000 to about3000. More specifically, these compounds are polyoxyalkylene compoundshaving terminal hydroxyalkyl carbamate groups, of the formula: ##STR3##wherein each R is, independently, hydrogen; or, a branched or straightchain alkyl radical of from 1 to about 6 carbon atoms, and morepreferably from 1 to about 4; X is hydrogen, a methyl radical or anethyl radical; Z is a hydrocarbon alkylene radical having 2 to 5 carbonatoms and n is a number selected such that the molecule of the aboveformula has a molecular weight of from about 2000 to 3000. The preferredpolyoxyalkylene compounds are of the above formula wherein R is hydrogenor a lower alkyl group, and more preferably a lower alkyl group of from1 to about 4 carbon atoms; X is a methyl radical; Z is a 1,2-propyleneradical; and n is a number from 16 to 19. Preferred lower alkyl groupsinclude methyl, ethyl, n-propyl and n-butyl.

The polyether dicarbamate compounds are formed by the reaction of ahydroxyalkyl carbamate compound with a polyoxyalkylene diamine having amolecular weight value such that the resultant dihydroxyalkyl carbamatecontaining product has a molecular weight of from about 2000 to about3000 at temperatures in the range from about 25° C. to about 150° C. ina molar ratio of about mole of hydroxyalkyl carbamate forming compoundsfor each mole of terminal amine.

The diamines that are useful in forming the additives arepolyoxyalkylene diamines of the formula: ##STR4## wherein X is ahydrogen, a methyl radical or an ethyl radical; Z is a hydrocarbonalkylene radical having from 2 to 5 carbon atoms; and, n is an averagenumber of from about 15 to about 25. Preferred polyoxypropylene diamineswherein X is a methyl radical, n is an average number from 16 to 19, Zis a 1,2-propylene radical. These polyoxyalkylene polyamines can beprepared by known methods as disclosed in U.S. Pat. Nos. 3,236,895 and3,654,370.

The hydroxyalkyl carbamate forming compounds are generally well known.They are generally those compounds which supply the O═C--O--CC--OHradical. Ethylene carbonate and alkyl substituted ethylene carbonatesare the preferred compounds.

In accordance with the method of forming the polyether carbamate, thereactants are simply admixed in correct molar ratios in a suitablereaction vessel and heated until the reaction occurs.

The functionality of the polyoxyalkylenepolyamine is dependent upon thenumber of terminal primary amino groups which in the instant case ispreferably 2. It will be realized that each mole of hydroxyalkylcarbamate forming compound will react with a single terminal primaryamino group of the polyoxyalkylenepolyamine. It is particularlyimportant that, in forming the additive compounds of the instantinvention, a specific molar ratio of reactants be maintained.Specifically, about 1 mole of hydroxyalkyl carbamate forming compoundfor each amino group of the polyoxyalkylenepolyamine is required. Thus,with the diamine, about 2 moles of hydroxyalkyl carbamate formingcompound is utilized. Preferably the instant reaction is carried out inthe presence of a slight excess of the hydroxyalkyl carbamate formingcompound to assure complete conversion of the amino groups.

Optionally, the epoxy resin formulations of the instant invention caninclude an "accelerator" to speed the amine cure of the epoxy resin,especially at ambient temperatures. In several applications, suchacceleration is beneficial, especially when an epoxy resin is used as anadhesive in flammable environment, thus making elevated temperature cureinconvenient or even hazardous. Lee, H. and Neville, K., Handbook ofEpoxy Resins, pp. 7-14 describes the use of certain amine-containingcompounds as epoxy curing agent-accelerators.

Many accelerators are known in the art which can be utilized inaccordance with the instant invention. Examples include salts ofphenols: salicyclic acids: amine salts of fatty acids such as thosedisclosed in U.S. Pat. Nos. 2,681,901; and, tertiary amines such asthose disclosed in 2,839,480. A preferred accelerator in accordance withthe instant invention is disclosed in U.S. Pat. No. 3,875,072 issued toG. Waddill, Apr. 1, 1975. The accelerator comprises a combination ofpiperazine and an alkanol amine in a weight ratio of about 1:8 to 1:1.

According to the method of the instant invention, the adhesionproperties of prior art amine-cured epoxy resins are enhanced by theaddition of an effective amount of a polyether dicarbamate havingterminal hydroxyalkyl carbamate groups and a molecular weight of fromabout 2000 to about 3000 as hereinbefore described. The amount ofadditive effective in bringing about the increase adhesive property issomewhat empirical and will depend upon the resin, the amine curingagent, and the use of an accelerator. Generally, the dicarbamateadditive can be utilized in amounts from about 5 to about 50 parts byweight based on one hundred parts by weight of the resin constituent.

Although somewhat empirical, the exact amount of additive used toincrease adhesion can readily be determined without undueexperimentation owing to the fact that a resin mixture containing aneffective amount of the additive will undergo changes which are readilyvisible as curing proceeds. Specifically, the curing resin takes on anopaque, milky white appearance that becomes more pronounced duringcuring and results in a product which has a lustrous white appearance.It will be realized that, advantageously, this optical absorption shiftenhances the beauty of cast objects and negates the need to use whitepigments or fillers.

Preferably the adhesive properties of prior art resins are enhanced byaddition of an effective amount of the polyoxypropylene dicarbamateadditive based upon the condensation of 2 moles ethylene carbonate with1 mole of a polyoxypropylenediamine having molecular weight of about2000. The preferred resins comprise polyglycidyl ethers of a polyhydricphenols cured by incorporating therein a curing amount of apolyoxyalkylenepolyamine of molecular weight from about 200 to 500 andan accelerator combination of piperazine and an alkanolamine, thecombination having a combined weight ratio of between about 1:8 to 1:1.Exemplary preferred prior art compositions can be enhanced in accordancewith the instant invention are disclosed in U.S. Pat. No. 3,943,104issued Mar. 9, 1976 to G. Waddill.

The curable epoxy resin compositions of the instant invention generallycomprise a vicinal polyepoxide, a curing amount of an amine curing agentand an effective amount of the polyether dicarbamate additive.Optionally an accelerator can be added.

The amine cured resins having superior adhesion in accordance with theinstant invention are prepared in a conventional manner. The aminecuring agent is admixed with the polyepoxide composition in amountsaccording to the amine equivalent weight of the curing agent employed.Generally the number of equivalents of amine groups is from about 0.8 toabout 1.2 times the number of epoxide equivalents present in the curableepoxy resin composition, with a stoichiometric amount being preferred.When using an accelerator, amounts from 1 to about 10 parts by weightbased on 100 parts by weight of the resin are generally satisfactory.The exact amount of constituents in accordance with the above generalrequirements will depend primarily on the application for which thecured resin is intended.

The dicarbamate additive is incorporated into the uncured resin byadmixing. Preferably, the additive is first admixed with the curingagent and/or the accelerator prior to addition to the resin. Theconstituents forming the curable material and then intimately admixed bystandard methods and degassed in the presence of a commercial defoamerand minute amounts of silicone oils to prevent voids and bubbles.

Although all of the epoxy resins disclosed herein are generally usefulin accordance with the instant inventive concept, those based onaliphatic compounds are preferably not used exclusively. The presence ofresins containing polyglycidyl ethers of polyhydric phenols in amountsgreater than 50% by weight of the resin constituent, and more preferably80% by weight and more preferably 100% by weight has been shown togreatly enhance the desirable properties of the cured material,especially the adhesive strength.

Likewise, although all of the disclosed amine curing agents aregenerally useful to cure the resin it has been found that those resinscontaining curing agents wherein the amino moieties are separated bylarge aliphatic or oxyalkylene chains do not demonstrate a substantialincrease in adhesive strength in the presence of the dihydroxyalkylcarbamate terminated additives. The exact reason for this is not fullyunderstood. For example, resins cured with polyoxypropylenediaminehaving molecular weights of above about 400, do not demonstrate greatlyenhanced adhesive strengths in the presence of otherwise effectiveamounts of the additives.

Preferred amine curring agents are those polyamines having amineequivalent weight of from 20 to about 70. Examples of such agentsinclude polyoxypropylenediamines having a molecular weight in the rangeof 200 to 300 and polyoxypropylenepolyamines having a molecular weightof from about 400 to 600.

It will be realized that those amine curing agents which are lesseffective in providing the adhesively superior resins can readily beavoided by the skilled artisan without undue experimentation, since suchagents do not effectuate the "optical shift".

In accordance with a preferred embodiment, a curable resin comprises adiglycidyl ether of 4,4'-isopropylidene bisphenol; a curing amount of aprimary amine-containing curing agent consisting essentially of apolyoxypropylene diamine having a molecular weight of from about 200 to250, an accelerator of piperazine and a triethanolamine in a weightratio of 3 to 7; and, an effective amount of a polyether dicarbamatehaving terminal hydroxyalkyl carbamate groups and a molecular weight ofabout 2000.

According to a greatly preferred embodiment, stoichiometric amounts ofthe resin and curing/accelerator composition are utilized. This amountis calculated by adding together the number of equivalents on the basisof weight per replaceable N-H group in the sum of the polyoxyalkylenepolyamine, piperazine and alkanolamine components utilized. Morepreferably, based on the above calculations, the curingagent/accelerator components are utilized in amounts which provide up toabout a 10% excess of the stoichiometric amount required based on theresin.

A preferred ratio of constituents comprises from about 1 to about 5parts by weight, per one hundred parts by weight of the resin, of apiperazine-alkanolamine accelerator in a weight ratio of between about1:8 and about 1:1 piperazine to alkanolamine. The above amount ofaccelerator is admixed with a polyoxyalkylenediamine curing agent inamounts of from about 10 to 50 parts by weight accelerator to 100 partsby weight of the polyoxyalkylene polyamine curing agent.

Generally, the mixture of epoxy resin, the polyether dicarbamate,polyoxyalkylenepropylene polyamine, and the accelerator combination ofpiperazine and alkanolamine is allowed to self-cure at ambienttemperatures of between 0° C. to about 45° C. However, it has been foundexpeditious that the mixture be cured or post-cured at elevatedtemperatures of up to about 135° C.

According to a greatly preferred embodiment, resins of the polyglydicylether of polyhydric phenol type are cured by incorporating therein abouta stoichiometric amount of a polyoxyalkylenepolyamine having a molecularweight of about 230; from about 5 to 40 parts by weight of the polyetherdihydroxyalkyl carbamate terminated polyoxyalkylenepolyamine having amolecular weight of about 2000; and from 1 to 5 weight percent based on100 parts by weight of the resin of an accelerator comprising a 30:70weight percent admixture of piperazine:triethanolamine. The compositionis cured at room temperature (about 25° C.) to produce products havingsuperior adhesive strength in accordance with the instant invention.

It will further be realized that various conveniently employed additivescan be admixed with the polyepoxide containing composition of theinstant invention prior to final cure. For example, in certain instancesit may be desired to add minor amounts of other polyalkyleneamineco-catalysts as herein described, or hardeners along with various otheraccelerators and curing agent systems well known in the art.

Additionally, conventional pigments, dyes, fillers, flame retardingagents and the like which are compatible, natural or synthetic resinscan be added.

Furthermore, although not preferred, known solvents for polyepoxidematerials such as toluene, benzene, xylene, dioxane, ethylene glycolmonomethylether and the like can be used. The polyepoxide resinscontaining the additives of the instant invention can be used in any ofthe above applications for which polyepoxides are customarily used. Oneoutstanding feature of the instant composition resides in the fact thatthey are opaque upon curing and give a smooth, white lustrous surfacewhich may be of particular benefit for certain molding and castingoperations. The compositions of the instant invention can be used asimpregnants, surface coatings, pottings, capsulating compositions,laminants, and, particularly and most importantly, as adhesives forbonding metallic elements or structures permanently together.

The following examples illustrate the nature of the instant inventionbut are not intended to be limitative thereof.

EXAMPLE I

In this example a polyether dihydroxyalkyl carbamate terminated additivefor use in accordance with the instant invention, was prepared. Into asuitable reaction vessel, equipped with stirring apparatus, were added1370 grams (0.72 moles) of a polyoxypropylenepolyamine having amolecular weight of approximately 2000, and an analysis of 1.01milliequivalents (meg.) primary amine/g sold under the tradename"JEFFAMINE®D-2000" by Jefferson Chemical Co., Austin, Texas 78751 and130 grams of ethylene carbonate (1.48 moles). The admixture was heatedfor several hours at 135°-150° C. The crude reaction product was thenvacuum stripped at 130°-175° C./1.4 mm Hg. Product analysis showed totalamine 0.21 meg/g, primary amine 0.19 meg/g, hydroxyl number 37.6.

To illustrate the advantage of the polyether carbonate additives of thisinvention, various epoxy formulations employing diglycidyl ether of4,4'-isopropylidene bisphenol were cured with various known polyaminecuring agents. Where indicated a commercial accelerator was utilized.Three drops of silicone fluid were added to each formulation to preventformation of voids and bubbles. After degassing under vacuum, theformulations were cured under the conditions indicated. In appropriateexamples, the cured products were subjected to standard American Societyfor Testing Materials (ASTM) tests for Izod impact strength (ASTMdesignation D-256), flexural strength and modulus of elasticity inflexure (ASTM designation D-790-66), tensile strength and elongation atbreak (ASTM designation D-638-64 T), deflection temperature (ASTMdesignation D-648-56) and hardness (ASTM designation 2240-64 T) and/orhardness Shore D, and peel strength (ASTM D-903). The tensile shearstrength (ASTM D-1002-64) was measured on adhesive bonds. All substrateswere aluminum panels (No. 2024-T-3 alloy, 16 gage), degreased, thenchromic acid etched prior to bonding. The abbreviations in the tables,pbw, psi and g. stand for parts by weight, pounds per square inch andgrams, respectively.

EXAMPLES II-VI

In these examples epoxy resins were prepared wherein diglycidyl ether of4,4'-isopropylidene bisphenol was cured with a polyoxypropylenediaminecuring agent of m.w. 230 having an equivalent weight of 58 to which wereadded the indicated amounts of the dicarbonate prepared in Example I.The resulting resins were used to bond aluminum to aluminum and theresultant subjected to the ASTM tests herein described. The data, whichare for comparative purposes only, is presented in the following TableI.

                  TABLE I                                                         ______________________________________                                                 Examples                                                             Formulation                                                                              2       3       4     5     6                                      ______________________________________                                        Epoxide, pbw                                                                  (Eq.190)   100     100     100   100   100                                    Curing agent, -pbw.sup.1)                                                                30      30      30    30    30                                     Dicarbonate, -pbw.sup.2)                                                                 0       2       5     10    20                                     Tensile shear,                                                                psi.sup.3) 980     1240    2830  3820  3770                                   Peel                                                                          strength.sup.3)                                                                          7.6     5.2     6.8   16.0  23.7                                   ______________________________________                                         .sup.1) Sold by Jefferson Chemical Company, Austin, Texas 7875l under the     name "JEFFAMINE.sup.®D-230                                                .sup.2) The product of Example I                                              .sup.3) Cure: 7 days, Room Temp.                                         

This example demonstrates the improved adhesion strength of the epoxyformulation when amounts of the bisureide are added to an epoxyformulation cured with a polyoxypropylenediamine of m.w. 230.

EXAMPLES VII-IX

In these examples the dicarbamate prepared in Example I was added to anepoxy system cured with triethylenetetramine at room temperature andcompared with a control system cured under the same conditions butwithout the additive. The formulations and properties of the curedresins are shown in Table II below. Considerable improvement in bondstrength can be observed in the resin which included the dicarbamate.

                  TABLE II                                                        ______________________________________                                                        Examples                                                      Formulation       7       8       9                                           ______________________________________                                        Epoxy, pbw (Eq.190)                                                                             100     100     100                                         Triethylenetetramine, pbw                                                                       12      12      12                                          Dicarbamate, pbw.sup.1)                                                                         --      5       10                                          Tensile shear strength, psi.sup.2)                                                              800     1520    1500                                        ______________________________________                                         .sup.1) Product of Example I                                                  .sup.2) Cures at room temperature for 7 days                             

EXAMPLES X-XV

In this example the diureide prepared in Example I was added in varyingamounts to amine cured systems. In two runs a polyoxypropylenediamine ofm.w. 400 and an amine equivalence of 105 was used and in two others apolyoxypropylenetriamine of m.w. 400 with an amine equivalence of about70. The results are shown in Table III below.

                  TABLE III                                                       ______________________________________                                                    Examples                                                          Formulation   10     11     12   13   14   15                                 ______________________________________                                        Epoxy, pbw (Eq. 190                                                                         100    100    100  100  100  100                                Curing agent (diamine)                                                                      50     50     50   --   --   --                                 pbw.sup.1)    50     50     50   --   --   --                                 Curing agent (triamine)                                                       pbw.sup.2)    --     --     --   45   45   45                                 Dicarbamate, pbw.sup.3)                                                                     0      10     20   10   20   0                                  Tensile shear strength,                                                       psi.sup.4)    2500   2660   2200 3030 3500 1400                               ______________________________________                                         .sup.1) Polyoxypropylenediamine sold under the tradename                      JEFFAMINE.sup.®D-400 by Jefferson Chemical Company, Austin, Texas         78751)                                                                        .sup.2) Polyoxypropylenetriamine sold under the tradename JEFFAMINE T-403     by Jefferson Chemical Company, Austin, Texas 78751                            .sup.3) Product of Example I                                                  .sup.4) Cured for 7 days at room temperature                             

This example shows that the additive is less effective in increasingadhesive strength when used in resins wherein polyether polyamine curingagents having an equivalence over about 70 is used.

EXAMPLES XVI-XVIII

In these examples the dicarbamate of Example I was added to an epoxysystem containing a diethylene glycol bis(propylamine) curing agent soldunder the tradename "ZZL-0822" by Union Carbide. The formulations andproperties of the cured resins are shown in Table IV below.

                  TABLE IV                                                        ______________________________________                                                    Examples                                                                      16      17       18                                               ______________________________________                                        Epoxy (Eg. 190)                                                                             100       100      100                                          Diethylene glycol -bis(propylamine).sup.1)                                                  30        30       30                                           Dicarbamate.sup.2)                                                                          --        5        10                                           Tensile shear, psi                                                                          1570      3280     3530                                         ______________________________________                                         .sup.1) Sold by Union Carbide Corporation, N.Y., N.Y. 10017 under the         tradename "ZZL-0822".                                                         .sup.2) Product of Example I.                                            

This example demonstrates the improved adhesive strength of the epoxycured with the additive over the epoxy cured with the diethylene glycolbis(propylamine) alone.

While the invention has been explained in relation to its preferredembodiment, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification and is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. An epoxy resin composition having superioradhesion properties and being the cured product of a curable admixturewhich comprises:a vicinal polyepoxide having an epoxide equivalency ofgreater than 1.8; a curing amount of a polyamine curing agent having atleast 3 reactive amino hydrogens; and, an effective amount of anadditive consisting essentially of a polyoxyalkylene dicarbamate havingterminal dihydroxyalkyl carbamate groups and a molecular weight fromabout 2000 to about
 3000. 2. The composition of claim 1 furthercomprising an effective amount of a composition effective inaccelerating the cure.
 3. The composition of claim 2 wherein saiddicarbamate is of the formula ##STR5## wherein each R is, independently,hydrogen; or, a branched or straight chain alkyl radical of from 1 toabout 6 carbon atoms; X is hydrogen, a methyl radical or an ethylradical; Z is a hydrocarbon alkylene radical having 2 to 5 carbon atomsand n is a number selected such that the molecule of the above formulahas a molecular weight of from about 2000 to about
 3000. 4. Thecomposition of claim 3 wherein each r is, independently, hydrogen or analkyl group having from 1 to about 4 carbon atoms; X is a methylradical, Z is a 1,2-propylene radical; and n is an average number from16 to
 19. 5. The composition of claim 3 wherein each R is,independently, hydrogen.
 6. The composition of claim 4 wherein each Ris, independently, a lower alkyl radical selected from the groupconsisting of methyl, ethyl, n-propyl and n-butyl.
 7. The composition ofclaim 2 wherein said vicinal polyepoxide is more than 80% by weight of apolyglycidyl ether of polyhydric phenols, wherein said polyamine curingagent is a polyoxyalkylene polyamine.
 8. The composition of claim 7wherein said vicinal polyepoxide is a polyglycidyl ether of a polyhydricphenol; wherein said polyamine curing agent is a polyoxyalkylenepolyamine having an amine equivalent weight of from 20 to about
 70. 9.The composition of claim 8 wherein said curing agent is selected frompolyoxyalkylene polyamines of the formula: ##STR6## wherein X ishydrogen, a methyl radical or an ethyl radical; Z is a hydrocarbonradical having 2 to 5 carbon atoms forming from 2 to 4 external etherlinkages; n is a number from 1 to about 15 and r is a number from 2 to4; or, the formula: ##STR7## wherein X, Z, n and r are defined as aboveand y is 2 or
 3. 10. A method for increasing the adhesive strength of anepoxy resin composition, being the cured product of a curable admixturecomprising a vicinal polyepoxide having an epoxide equivalency ofgreater than 1.8; and, a curing amount of a polyamine curing agenthaving at least 3 reactive amino hydrogens comprising the step of:addingto said curable admixture an effective amount of a polyoxyalkylenedicarbamate additive having a molecular weight of about 2000 to about3000.
 11. The method of claim 10 wherein said dicarbamate is of theformula ##STR8## wherein each R is, independently, hydrogen; or, abranched or straight chain alkyl radical of from 1 to about 6 carbonatoms; X is hydrogen, a methyl radical or an ethyl radical; Z is ahydrocarbon alkylene radical having 2 to 5 carbon atoms and n is anumber selected such that the molecule of the above formula has amolecular weight of from about 2000 to about
 3000. 12. The method ofclaim 11 wherein each R is, independently, hydrogen or a lower alkyl; Xis a methyl radical; Z is a 1,2-propylene radical; and n is an averagenumber from 16 to
 19. 13. The method of claim 12 wherein each R is,independently, hydrogen.
 14. The method of claim 13 wherein said curableadmixture further comprises an effective amount of a compositioneffective in accelerating the cure.
 15. The method of claim 13 whereinsaid curing agent is selected from polyoxyalkylene polyamines of theformula: ##STR9## wherein X is hydrogen, a methyl radical or an ethylradical; Z is a hydrocarbon radical having 2 to 5 carbon atoms formingfrom 2 to 4 external ether linkages; n is a number from 1 to about 15and r is a number from 2 to 4; or, the formula: ##STR10## wherein X, Z,n and r are defined as above and y is 2 or
 3. 16. A curable resincomposition comprising a diglycidyl ether of 4,4'-isopropylidenebisphenol polyepoxide; a curing amount of a primary amine-containingcuring agent consisting essentially of a polyoxypropylene diamine havinga molecular weight of from about 200 to 250, an accelerator ofpiperazine and a triethanolamine in a weight ratio of 3 to 7; and, aneffective amount of a polyoxyalkylene dicarbamate having terminaldihydroxyalkyl carbamate groups and a molecular weight of about 2000.17. The resin of claim 16, wherein said primary amine-containing curingagent is present in about a stoichiometric amount; said accelerator ispresent in amount from about 1 to 5 parts by weight based on 100 partsby weight said polyepoxide, said additive is present in amount fromabout 5 to 40 parts by weight based on 100 parts by weight of saidpolyepoxide.